Hydraulic power brake



lme 24, 1941. H. D. COLMAN 2,245,667

HYDRAULI C POWER BRAKE Filed May 8, 1957 4 Sheets-Sheet l June 24,1941. H. D. coLMAN HYDRAULIC POWER BRAKE Filed May 8, 1937 4 SheetS-Sheet 2 HNVNTGF: Howard l). C0 imam June 24, 1941. H. D. COLMAN HYDRAULIC POWER BRAKE Filed May '8, 1957 4 Sheets-Shee'rI 5 l f INVENTOR #awa/d June 24, 1941. H, D- COLMAN 2,246,667

HYDRAULI C POWER BRAKE Filed May 8, 1937 4 Sheets-Sheet 4 INVENTOR Hou/ara' D. Colman BY @dA/n; z- A TORNEY Patented June 24, 1941 HYDRAULIC POWER BRAKE Howard D. Coleman, Rockford, Ill. Application May 8, 1937, Serial No. 141,432

7 Claims.

The present Ainvention relates to hydraulic power brakes and has particular reference to a new and improved brake adapted for automotive vehicles.

One o'f the primary objects of the present invention is to provide a novel hydraulic power brake having a closed liquid system hermetically sealed at all .points from the atmosphere.

Another object is to provide a new and improved hydraulic power brake in which all of the movable elements exposed to the brake liquid and to the atmosphere are yieldably connected by means of hermetically sealed rubber bellows or diaphragms to the relatively stationary elements so las to avoid the loss of liquid by leakage and the infiltration of air.

A general object is to provide a novel hydraulic power brake which is simple and inexpensive in construction and eflicient and reliable in operation, which is manually controllable with the expenditure of a small force to effect a progressive braking action, and in which the manual control is subjected to a proportionately small hydraulic reaction imparting a feel to the operator varying in accordance with the braking pressure.

Still another object is to provide a new and improved hydraulic power brake which is easy to assemble and disassemble and in which all internal parts are readily accessible for inspection,

' repair and replacement.

manual actuation.

Further objects and advantages will become apparent as the description proceeds.

In the accompanying drawings, Figure 1 is a perspective view of a power braking system embodying the features of my invention and adapted particularly for automotive vehicles.

Fig. 2 is a fragmentary side elevational view of a manually operable control unit forming part of the system.

Fig. 3 is a longitudinal vertical sectional view on an enlarged. scaleof the control unit.v

Fig. 4 is a fragmentary transverse sectional view taken substantially along-line `414-4. of, g, 3. Fig. 5 is a fragmentary side elevational-f-view partially in sectionv in the same planefasvFigv.- 3, but illustrating the parts in a different: position of adjustment.

Fig. 6 is a. fragmentary, detailed sectional view taken substantially alongqlinenG-f-E of Fig-.3Q-;.:; Fig. Tis a fragmentary longitudinal sectional view of a combination sump and rpump ,Y unit forming part ofthe systemw@ i Fig. 8 is a fragmentary `plan viewofthe sump and pump unit. I Y Fig. 9 is a perspective view of a device or'controlling the operativeness of. the :pump..,y f

Fig. 10 is a fragmentary sectionalview taken substantially along line Ill-,I0 of Fig.,8.` y

Fig`.11 is a vertical `sectionalview of a pressur reservoir forming part of the system.A Fig. 12 is a fragmentary perspective viewillustrating certain parts of the reservoirinfdisas- Referring more particularly to .the; y drawings, the power brake system, 4constituting theexam plary embodimentfof,theinvention, is adapted particularly for automotive vehicles, `suon-for exl ample, as automobiles, trucks'andbussespand inv such application .would ordinarily comprise four hydraulically operable wheel brakes I3, ,It

Ais to be understood, however,thatthesystem is control of` a unit I6 which ris operablemanually,

as by` a foot pedal I'I pivotedintermediategits ends at I8, and which is radapted to'conneotthe lineI5 either to a relief line I9 leading to a sump 20 forV and duringbrakerelease,orto a pressure line 2l` leading from vasuitablesourceaoi'iliquid under pressure for brake application, V- Themnit I6 is also operable automaticallyr during brake application to trap the brake liquid` inthe line`|5 at different pressures corresponding to progressive positions of fadjustmen'tgof ythe vfootpedal I1, and to impose a resistanceto movementgof the pedal less thanbutproportionaleto thexpresf sure. Hence, the unit I6'fhas la .follow-upfunction permitting application of the brakes I3 with any desired pressure, and imparts a "feel to the operator whereby the brake pressure, although transmitted from a power source, may be sensed. The pressure source may be an `accumulator or reservoir 22 connected to the line 2I, and adapted to be kept supplied with brake liquid within a predetermined pressure range by a pump 23 taking liquid from the sump 2II. In the present instance, the pump 23 is driven continuously from the vehicle engine, illustrated in dotted outline at 24, and is self-controlled to discharge liquidas required. l

The control unit The control unit I6 (see Figs. 2 to 6) comprises a main body 25 which may be mounted in any suitable position onrthevehicle, and which is formed with an internal chamber 26 connected through one wall to the line I leading to the various brake actuators I4. The chamber 26 opens to one side oi' the body 25, and is normally closed by. a removable cover plate 21. A gasket 26 is interposed between the body 25 and the plate 21 to provide a tightseal. A valve housing 29 is removably mounted on the body 25, and encloses a normally closed pressure inlet valve 3U for connecting the line 2| to the control chamber 26, and a spring seated relief valve 3| for connecting the chamber through the line I9 to the sump ZII. A suitable gasket 32 is interposed between the body and the housing 29 to provide a tight seal.

The pressure valve is operatively mounted in a valve chamber 33 connected to the outlet end of the line 2| (see Fig. 2), and formed in the lower side of the housing 29 for communication through a valve bore or passage 3.4 in the body 25 with the top of the chamber 26. In its preferred form, the pressure valve 30 comprises an annular valve seat 35 formed in the body 25 at and about the inlet end of the passage 34, and an axially movable valve member 36 normally urged by a coiled compression spring 31 into engagement with the seat.

The valve member 36 consists of a sealed cup, of a suitable yieldable or resilient material, such, for example, as elastic rubber or rubber compolength is relatively small, and since the spring 31 is quite still', the spring convolutions may be closely spaced, and tend to resist unequal relasition, having a cylindrical or tubular wall supported against radial deformation by external pressure and adapted for axial elongation and contraction, and having a closed end vwall delining a yieldable valve face 33. The open end of the cup 36 is connected with a hermetic seal -to the valve housing 29, and to this end is formed with an enlarged outer peripheral rib or bead 39 seated in an annular groove 40 in the inner end face of a closed bore 4I opening to the top of the chamber 33. A washer 42 is clamped against the outer edge ofthejgroove 40 by a ring nutj43V threaded into'thejgbore-.4I to confine the bead 39 under a 'deilection pressure. A circular plug 44, with'an inner axial stem 45, is seated in the closed end of the cup 36, and serves to reenforce the valve face 38 and to maintain the area thereof substantially constant. The spring* 31, which is formed of a square wire, is seated at the upper end against the bottom of the b ore 4I, and at its other end engages the plug 44 with a predetermined force tending to elongate the cup 36 and thereby to close the valve 3l). The spring 31 also serves to reenforce the peripheral wall of the cup 36 against the liquid pressure in the chamber 33.` Since the range of axial elongation of the bellows 36 in relation toits tive displacement, so that the spaces between the convolutions are suiliciently restricted to prevent intrusion of the rubber. Anchored in the housing 29 and extending through the spring 31 into telescoping relation with the stem 45 is a tube 46 which serves to prevent buckling of the spring, and which acts as a stop adapted for engagement by the plug 44 to limit the opening movement of the valve 30.

The cup or valve member 36 in effect constitutes a valve bellows having a constant effective internal end area substantially the same in size as the effective area circumscribed by the valve seat 35. 'I'he interior of the cup or bellows 36 is always in free communication with the control chamber 26 through the tube 46 and interconnecting passages 41 and 43 in the valve housing 29 and the body 25, and hence the liquid pressures acting against the inner and outer sides of the movable end wall 36 are substantially equal. The valve member 36 therefore is substantially liquid pressure balanced, and adapted to be lifted by a force Suilicient only to overcome the pressure of the spring 31 which, of course, should lie-adequate to prevent leakage when the valve 30 is closed.

'I'he relief valve 3| is generally similar to the pressure valve 30, and is operatively mounted in a valve chamber 49 connected at one side to the inlet end of the line I9 (see Fig. 2), and formed in the lower side of the housing 29 for communication with the chamber 26 through a valve bore or passage 5D in the body 25. In its preferred form, the exhaust valve 3l comprises an annular valve seat 5I formed in the body 26 at and about the discharge end of the passage 59, and an axially movable valve member 52 normally urged by a coiled compression spring 53 into engagement with the seat.v Ihe valve member 52 comprises a sealed cup or valve bellows of a suitably yieldableI or resilient material, such, for example, as elastic rubber or rubber composition, having a cylindrical or tubular wall supported against radial deformation by internal pressure and adapted for axial elongation and contraction. The open end of the bellows 52 is connected with a hermetic seal to the valve housing 29 for free communication internally with the bore 41, and to this end is formed with an enlarged peripheral rib or bead 54 which is seated in an annular groove 55 in the end face of a bore 56 opening to the top of the chamber 49 and which is clamped therein under deection pressure by means of a washer 51 and a ring nut 58. l i

The movable end of the bellows 52 is provided -with an inner peripheral ilange in th'e form of an enlarged rib or bead 59 seated internally in an annular groove 66 in a disk 6I having an axial stem 62. An apertured outer disk 63 slidably interfits with thestem 62, and is secured thereon by means of a washer 64 held in place by a screw bolt 65 to clamp the bead 59 in the groove under deflection pressure. An insert 66 of resilient material, such, for example, as a rubber washer defining a valve face, is secured by the washer 64 in an annular recess 61 in the outer disk 63. The coiled compression spring 53, which is made of square wire turned into closely spaced relatively stiff convolutions, encircles the peripheral wall of the bellows 52 to reenforce the latter against radial enlargement by the internal pressure, and is confined under compression between the washer 51 and an annular ange 68on the outer disk 63. An external antibuckling tube 68 for the spring 53 is clamped at one end between the washer 51 and the nut 58, and at the other end telescopes slidably with the flangev 68 to guide and linut the opening movement of the valve member 52.

The pressure and relief valves 38 and 8| areI effect closing of the pressure valve 38 and thereby trapping of the liquid in the brake actuators I4.

The valve actuating mechanism comprises two lifter tappet members 18 and 12 which are slidable respectively in the -valve passages 34 and 50 for engagement at their upper or outer ends with the valve face 38 and the washer 64, and which are provided at their lower or inner ends with abutment heads or disks 1| and 13 engaging at their undersides with the upper sides of the rounded ends of a generally horizontal pivotal lever 14. Each of the tappet members 18 and 12 may be constructed of two flat sheet metal plates secured together at right angles by inter- 'l fitting longitudinal slots to define quadrant vanes permitting an unrestricted flow of liquid, and secured at their inner ends as by means of riveting to the associated head 1| or 13.

The tappet lever 14 is pivotally lmounted midway of its ends on a pin 15 within a slot 16 formed in a movable block 11. The-arrangement is such that when the lever 14 is disposed in a horizontal or neutral position both valves 38 and 3| will be closed, and when it is oscillated out of neutral position, the valves will alternately be opened and closed respectively. Opening longitudinally to one end of the block 11 and intersecting the arcuate root of the slot 16 is a bore 18. A rod 18 is slidably disposed at one end in the bore 18, and extends loosely through a bore 88 in one end wall of the chamber 26 for operative association with the brake pedal I1. The lever 14 is in the form of a double bell crank having a short depending third arm 8| engaging in a peripheral notch 82 in the inner end of the rod 18. It will be evident that axial movement of' the rod 18, with the block 11 stationary, will effect actuation of the valves 38 and 3| to apply or release the brakes I3.

The operative connection betweenV the brake pedal i1 and the rod 18 comprises a cup-shaped member having a closed end wall 83 and having a cylindrical wall 84 slidable in an external cover tube 85 and telescoping loosely with the open end of a concentric internal tube 86. The cover tube 85 is bolted at one end to the body 25 of the control unit I6, and is turned in at the other end to define a stop 81 for limiting the outward movement of the member 83, 84. The inner tube 86 is rigidly secured at one end by an encircling ring nut 88 in a counterbore 88 in the body 26 about the bore 88. A coiled compression spring 88, between the tubes 85 and 86, is seated at one end in a centering notch 8| in the nut 88 and at the other end in a centering notch 82 in the free end of the wall 84, and tends to urge the member 83, 84 outwardly.

A brake rod 83 is suitably connected at one end to the pedal I1, and at the other end is rounded and in engagement with a ball socket 84 in the end wall 83. A sealing bellows 85 attached at opposite endsA to the tube 85 and the brake rod 83 serves to exclude the oxygen ofthe air and solid foreign matter. The spring 88, acting through the member 83, 84 and the rod 83, acts to return the pedal I1 to inoperative position during brake release.

Thesouter end of the rod 18 extends ooncen.- trically through the vtube 86, and is rigidly attached to a circular head or disk 86 removably fixed in an interfitting recess 81 in the inner face of the wall 83 for movement therewith. In the present instance, the disk 86 is apertured to receive an axial stud 88 on the rod 18, and is clamped by a suitable nut 88 against an annular shoulder |88 at the base of the stud. A pedal bellows |8| exposed internally to the liquid pressure in the control chamber 26 tends. to urge the disk 86 outwardly.

The pedal bellows |8| comprises an elongated cylindrical wall which may be made of any suitable resilient material, such, for example, as rubber or rubber composition, and which is reenforced against diametrical enlargement and is axially extensible and contractible in accordance with the movements of the rod 18. Opposite ends of the bellows |8| are connected with vahermetic seal respectively to the body 25 and the outer 'end of the rod 18. Preferably, the fixed or inner end of the bellows I 8| is formed with an external peripheral flange which is enlarged to provide a thick rib or bead |82, .and which is seated in an annular groove |83 in the end of a counterbore 88 concentrically about the bore 88, The bead |82 is clamped in the groove |83,under a heavy deflection pressure by an overlying washer |84 suitably rounded at the inner .edge t0 present a smooth surface to the rubber. A An anchor ring |85 and an annular flange |86 on the inner end of the tube 86 are clamped in superimposed relation against the washer |84 by the ring nut 88. The outer or movable end of the bellows |8| is formed with an inner peripheral flange which is enlarged to provide a thick rib or bead |81, and which is clamped under a heavy deflection pressure by the disk 86 in an annular groove |88 formed in the shoulder |88. Preferably, the outer lip of the groove |08 is flared, as in a metal .f upsetting process, to a diametergreater than that of the rod 18 and serves to confine the end of the bellows wall against the interior of an encircling annular flange |88 on the disk 86,

Interposed between the tube 86 and the bellows wall is a tubular reenforcement I I8 substantially rigid diametrically and readily extensible and contractible axially. The reenforcement ||8 may be of any suitable construction, and preferably comprises a plurality of axially aligned rings interlocked to limit theextent of axial separation as disclosed in my aforesaid copending application. Opposite ends of the reenforcement |I8 are nonrotatably anchored respectively to the spacer ring |85 and the ange |88 on the head 86. The reenforcement ||8 isvconned against buckling by the tube 86, and serves to support the bellows wall against diametrical enlargement by the internal pressure, and thereby maintain a constant annular bellows piston area about the rod 19 always open through the bore Il to the liquid pressureinthechamber 29.

The valves 39v and 3| are also adapted to be actuated by the block 11 independently of the brake pedal |1. In the present instance, the block 11 is rectangular in cross section, and is conned at the top against rotation and for close sliding adjustment longitudinally of the rod 19 by two parallel guide surfaces and ||2 respectively on the cover plate 21 and the opposed side wall of the control chamber 29 (see Fig. 4). These surfaces servealso to conne the pin 15 within the block 11. One end of the block 11 is formed with a transverse T-slot ||3 open to the inner end of the bore 13. The lips of the T-slot ||3 engage in an annular -groove ||4 formed in the inner end portion of a rod' ||5 axially aligned with the rod 19 and extending slidably with a close tting through a bore ||9 in the adjacent end wall ofthe chamber 29 for external actuation. Preferably, the inner end of the rod ||5 is formed with an axial bore ||1 slidably telescoping with an extension of reduced diameter on the inner end of the rod 19. As a result, both rods 19 and ||5 are'guided laterally by the block 11, and the block and the inner en'd of the rod 19 are supported by the rod ||5. It will be evident that, in any position of adjustment of the rod 19, axial-movement of the rod ||5 will shift the block 11, and thereby. eil'ect oscillation of the lever 14 about thenotch 92 as a stationary fulcrum to actuate the'valves 3|! and 3|.

'I'he rod ||5 is adjustable by a pressure responsive element ||8 acting in opposition to a coiled tension spring ||9 to eifect movement of the lever 1.4 into neutral position whenever the brake liquid in the chamber 26 attains a predetermined pressure varying in accordance with the position of the brake pedal |1. In the present instance, the element ||8 is in the form oi' a rubber bellows, appropriately designated as a pressure control bellows, and comprising a cylindrical wall extending in concentrically spaced relation about the outer end portion of the rod`| |5. The bellows ||8 is attached with a hermetic' seal at opposite ends respectively to the body 25 of the control unit for internal communication with the control chamber 26 through longitudinal grooves |20 cut in the periphery of the bore ||6 (see Fig. 6). and tothe outer end of the rod- ||5 to define an annular internal piston area. The cylindrical wall of the bellows ||9 is confined against diametrical enlargement by the liquid pressure so as to maintain the piston area lconstant, and is axially extensible and contractible in response to the liquid pressure variations.

To provide a suitable seal and anchor, the xed or inner end of the bellows 8 is formed with a peripheral flange |2| which is enlarged to provide an annular rib or bead, and which is seated in an annular groove |22 in the end wall of a counterbore |23 about the bore IIS. The ilange |2| is clamped in the groove |22 under a heavy deilection pressure by a washer |24 which is rounded at the inner edge to present a smooth surface to the rubber. An anchor ring |25 and a ilange |26 on the inner end of a tube |21 extending concentrically along the bellows ||8 are superimposed on the washer |24, and the assembly is clamped against the end wall of the counterbore |23 by a ring nut |28.

At the movable or outer end, the bellows ||3 is provided with an internalilange |29 which is enlarged to form an annular rib or bead, and

-end of the tube |21.

which is seated in an annular groove |39 formed in the end of the rod ||5 inwardly of a shoulder |3| at the base of an axial stud |32. Ach-cular piston head or disk |33 is secured against the shoulder |3| by a nut |34 on the stud |32, and serves to clamp the rubber ange in the groove |39 under a heavy deection pressure. The outer lip oi.' the groove |39 is struck outwardly in a metal upsetting process, and serves to coniine the outer end of the wall against an encircling annular ilange |35 on the disk |33.

Interposed between the bellows ||8 and the tube |21 and nonrotatably anchored at the ends to the ring |25 and the ilange |35 is a diametrically rigid and axially extensible and contractible reenforcement |36 similar to thereenforcement H9. The reenforcement |35 is held against buckling by the tube |21, and supports the bellows ||9 against the internal liquid pressure to maintain a constant annular pressure area about the rod ||5 and subject at all times through the grooves |29 to the pressure in the chamber 26.

The bellows head or disk |33 is removably held in a closely fitting circular recess |31 formed in the inner face of the end wall |38 of a cup-shaped member |39. This member has a cylindrical wall slidably telescoping with the outer end of the antibuckling tube |21, and serves as a guide for the outer end .of the rod 5. 'I'he coiled tension spring ||9 is' anchored' at opposite ends to the ring nut |28 and the member |39, and tends to urge the latter inwardly. Each anchor may be eifected by threading the end coils into interlocking engagement. Inward movement of the member |39 is limited by the .The spring ||9 has a strength when contracted 'only slightly higher than necessary to overcome the sump pressure, and when expanded suilicient to balance the maximum brake pressure.

The pressure bellows ||8 and associated parts just described are enclosed to exclude foreign matter and to prevent oxidation of the rubber and lubricant. The enclosure consists of a tube |40 bolted at one end to the unit body 25, and a rubber cup |4| telescoping with the outer end of the tube |49, and is clamped thereto at the rim.

When the brakes are released, the parts of the control unit I9 are positioned as illustrated in Fig. 3, the pressure valve 3|! being closed, and the relief valve 3| being open. Upon actuating the foot pedal |1 to apply the brakes i3, the rod 19 is moved inwardly, thereby rocking the lever 14 in a counterclockwse direction through neutral position, in which both valves 30 and 3| are closed (see Fig. 5), into the position in which the relief valve 3| is closed -and the pressure valve 39 is open. Brake liquid under pressure is now admitted to the control chamber 26, and from there passes to the various brake actuators |4 to apply the brakes. As the pressure in the control chamber 26 rises, the pressure control bellows ||9 is elongated against the action of the tension spring H9, thereby moving the rod ||5 and block 11 to the right to rock the lever 14 in a clockwise direction. The bellows head |33 seeks a position of balance in which the tappet lever 14 occupies a neutral position to close the pressure valve 30 and thereby prevent any further rise of pressure in the control chamber. 'Ihe pressure at which this will occur depends on the position of the brake pedal |1, and increases as the pedal is progressively depressed. If the `advancing movement of the pedal |1 has been limited to iiange |45 dening a circular recess |46.

permits application of the brakes with anyv cle-V sired pressure, and this pressure reacts on the pedal bellows |6| to'v impart a corresponding feel to the foot of the operator.

The action is reversed upon brake release. Upon return of the foot pedal, the lever 14 is rocked in a clockwise direction to open the relief valve 3| and permit the escape of the brake liquid. As the pressure drops, the bellows head |33 moves to the left, and tends to rock the bell crank in a counterclockwise direction to close the relief valve if the lbrake pedal I1 is only partially released. When the brake pedal is fully released, the bellows head |33 is limited against further inward movement by the tube |21 so that the relief valve 3| will remain open.

If the brake pedal I1 is depressed rapidly, the movable head |33 of the bellows IIB may not always respond to actuate the rod I|5 at the same rate. In this event, the end of the rod 19 will strike the bottom of the bore ||1 to transmit the excess pedal pressure directly to the spring ||9, thereby preventing excessive strain on the bell crank lever 14. Whenever this happens, the feel of the pedal I1`will not correctly represent the pressure against the brakes, but this is due -only to a momentary delay in the transmission of force and is immediately cor`- rected. When the brade pedal |1 reaches the limit of forward movement'as determined by engagement of the cup-shaped member 83, 84 with the end of the antibuckling tube 86, the feel of the pedal I1 will not represent the pressure on the brakes, but this condition will` The sump The sump `(see Figs. '1, 8 vand 10) has a chamber |42 which is automatically variable in size so as to be filled with liquid at all times, and which is under compression so as to maintain a low initial or residual pressure.

In its preferred form, the sump 20 comprises a body |43 having amounting ange or bracket |44 adapted to'be removably bolted to a support, such as the engine block 24 of the vehicle. The body |43 is generally cylindrical in shape, and is provided at one end with a projecting annular A yieldable diaphragm, of a suitable material such as elastic rubber or rubber composition, and preferably in the form of a cylindrical axially extensible and contractible bellows wall |41, is connected at one end with a hermetic seal to the ange |45 and is closed at the other end with a rigid movable head- |48. In the present instance, the inner end of the diaphragm or wall 41 is formed with a peripheralange |49 disposed within an annular notch in the inner peripheral edge of the outer end of the body ange |45. An outer perpheral rib or bead 5| on 'the rubber ilange |49 is seated in an annular groove |52 formed in the radial wall of the notch |50. The bead |5| is clamped within the groove |52 under a heavy deflection pressure by an overlying annular disk |53 secured in position against the bottom of the notch |50. superimposed against the disk |53 is an anchor ring |54 and an outer peripheral nange |55 on the rim of a cylindrical cup or housing |56. The assembly of the disk |53, ring |54 and cup flange |55 may be tightly secured within the notch |50 by any suit- .able means, as, for example, by riveting or upsetting the metal of the body flange |45 as indicated at |51.

The bellows head |48 is, slidable in the housing |56, and has an annular peripheral ange |58 encircling the outer end of the bellows wall |41. An inner peripheral ange |59 on the' ,bellows wall |41 is seated in an annular groove |60 in an inner disk |6I. The flange |59 is thickened to form a rib` or-bead, and is clamped under deection pressure by securing the disk |6| to the inside of the head |48. Disposed in the space between the bellows wall |41 and the I housing |56, and'nonrotatably anchored at opposite ends to the anchor ring |54 and the flange |58 is a reenforcement |62 of the same general character as the reenforcements ||0 and |36. The reenforcement |62 is held against buckling by the housing |56, and serves to support the wall |41 against diametrical enlargement by the internal sump pressure.

A coiled tension lspring |63 is anchored at opposite ends respectively to ,the body |43 and the inner disk |6I, and tends to contract the bellows |41. To provide a suitable anchor, the inner end convolutions of the spring |63 are threaded in interlocking engagement into an annular plate |64 secured as by screw bolts |65 against the bottom of the recess |46, and centered by the ange |45. The other. end convolutions of the spring |63 are threaded in interlocking engagement onto the inner disk I6|.

The interior of the bellows |41 and the recess |46 dene the sump chamber |42 which, as will be evident, is contractible by the spring |63 to maintain the desired liquid pressure, and which is expansible as required to receive the liquid discharged from thev control unitv I6 upon brake release. To establish communication with the control unit, the recess |46 opens through a passage |66 to a receiving chamber |61 of irregular shape formed in the opposite end of the body |43. The discharge end of the line I9 is connected to and opens through a cover plate |68 which is bolted to the body |43 and closes the receiving chamber |61. A gasket |69 is positioned between the body |43 and the cover plate |60 to The pressure iiuid medium for operating the brakes I3 is supplied to the conduit or line 2| leading to the control unit I6 from the pressure reservoir 22 (see Figs. 11 and 12).

The reservoir 22 comprises a closed tank of a suitable rigid material, such, for example, as forged steel, substantially impervious to the passage of gases and liquids. A iiexible partition or diaphragm |69 separates the interior ofthe tank into a chamber or space |10 adapted to receive the 'brake liquid, and a second chamber or space |1| containing a hermetically sealed body of gas underpressure. The diaphragm |69 also is made of a suitable material, such, for example, as rubber, substantially impervious to the passage of gases and liquids. The sealed body of gas is not in contact with the brake liquid and hence liquid under pressure regardless of the degree to which the reservoir is illled.

The tank 22 'may be provided in various forms, and preferably comprises two oppositely disposed cups |12 and |13 suitably connected together at the rims. A suitable gasket |13 is interposed between ythe cups |12 and |13 to provide a liquidtight seal. The cup |12 constitutes a tubular reservoir body which is rounded or semi-spherical at the closed end. The other cup |13 is semispherical in form, and serves as a cover having an annular marginal flange |15 removably threaded onto the open end of the body |12.

The tank 22 is normally supported in a horizontal position, and has an integral stem |13 projecting from a fiat annular shoulder |11 and formed with an axial bore |13V opening centrally through the cover |13. The stem |13 is formed intermediate its ends withl an external peripheral groove |13 and a plurality of radial ports |33 opening therefrom to the bore |13. A gasket |3I with a central sleeve |32 is slidably disposed on the stem |13 immediately above the groove |19 and against the shoulder |11. Positioned on the sleeve |32 and against the gasket |3|, and freely encircling the stem |13 in the region of the groove |13 is a tubular line connecter or tting |33 with an internally threaded boss |33 on one side. A branch end of the liquid inlet and discharge line 2| is removably secured in the boss |33 with a liquid-tight seal by a gland nut |35, and opens through a port |33 to the interior of the fitting |33 for icommunication with the groove |13. The fitting |33 is pressed tightly against the gasket |3| by a cap nut |31 threaded onto the free end of the stem |13. Interposed between the fitting |33 and'the nut |31 is a gasket |33. vIt will be understood that the gaskets |3| and |33 provide a liquid-tight seal in the connection between the stem |13v and the fitting |33.

The partition or diaphragm |33 preferably is provided in the form of a sealed rubber bag disposed substantially entirely within the tank 22 and having a sealed filling stem |33 projecting into the bore |13. '111e space between the inner surface of the tank 22 and the exterior ot the bag |33 constitutes the liquid chamber |13, and the interior of the bag defines the gas'chamber |1|. The bag has a free form of such size and shape that it will fit loosely within the tank 22, but upon the application of a slight amount of internal pressure will stretch readily to press against tie inner walls of the tank, assuming the latter to' be empty of liquid. Since the gas is not in direct contact with the wall of the tank 22 but is conned in the bag |33 immersed in the brake liquid, it cannot leak out by permeation through the .pores of the metal, Also, it will have little or no tendency to permeate through the wall of the bag |33 since the opposite sides of the wall are normally subjected to equal pressures. Consequently, the reservoir will hold the gas under a heavy pressure without leakage or objectionable pressure loss for a long period of time, running into years. 'Y

Seated in and conforming to the interior of the cover |13 is a semi-spherical cup |33 which preferably is integral with the gasket |13, and which at the center is pierced and drawn into a short iiared boss |3| projecting into a counterbore` |32 at the inner end oi the bore |13. An elongated tube |33 extends through the boss |3| with a nt sufiiciently close to eifect a mechanical connection but not necessarily liquid-tight. and projects therefrom in concentrlcally spaced relation into the bore |13 to receive the lling stem |33. The upper end portion of the tube |33 is iiared to interilt with the inner surface of the 'boss |3|, and the wall thereof is gradually tapered to merge with the inner surface of the cup |33 so as to present a smooth surface to the bag |33. It will be understood that the tube 33 serves to prevent the stem |33 from being inated into engagement with the wall of the bore |13 which if permitted would close the liquid passage through the bore and at the ports |30.

The liner cup |33 is formed with a plurality of small ports |33 which open about the boss |3| to the counterbore |32 so as to maintain unrestricted communication between the interior of the tank 22 and the bore |13 about the tube |33. The holes or ports |33 are suiiiciently small in relation to the thickness of the wall of the bag |63 to prevent the gas pressure from forcing entry of the rubber therein to an objectionable extent. Snugly seated in the counterbore |32 and having a central flared aperture |35 receiving and'intertting with the boss |3| is a disk |33 defining a plurality of passages for connecting the ports |33 to the bore |13. In the present instance, the disk lss is formed with annular notches' |31 and |33 in its outer edges, with peripherally spaced grooves |33 as by hobbing connecting the notches, and with radial grooves 233' in the lower face. opening from the notch |33 to the aperture |35 for communication with the upper end of the bore |13.

In the assembly operation, the rubber bag |33 is iniiated through the stem |33 with a suitable gas under a pressure sufficient to give the required minimum or residual pressure when the tank 22 is empty of liquid. At this time, the stem |33 is unsealed and projects out of the bore |13 for attachment to a suitable source of gas (not shown). After the bag |33 is lled, the rubber stem |33, while being stretched and clamped temporarily, is vulcanized at the end of the stem |13 to seal in the gas, and then the excess length beyond the seal is out olf. A ap 23| within the bag |33 temporarily closes the inner end of the stem |33 during the sealing operation. The sealed stem 33 is of such length that, in its uninflated or free form, the end would reach the nut |31. When inflated, the stem |33 will tend to become somewhat elongated, but will be held in position by a plug 232 in the outer end of the bore |13.

Upon ination of the bag |33, substantially all of the air in the tank 22 will be removed. A small amount of air may remain initially in the bore 13 about the tube |33 and in the passages of the disk |33, but this air can be readily removed by evacuation and replaced by liquid.

The assembly 'being completed, brake liquid may be supplied from a suitable source under pressure through the line 2|. When the pressure in the line 2| rises above the residual gas pressure, liquid will ow into the chamber |13, and will compress the gas to collapse the bag |33 progressively as required. Except when the tank 22 is empty, the bag |33 is immersed in the liquid, and. subjected to substantially the same pressure at the inside and outside, so that there is no tendency of the gas molecules to escape through the walls of the bag.

The pump Brake liquid is supplied to the pressure reser- .voir 22 by the pump 23 as required to maintain 2,24c,eev

a 1 predetermined availablepressure. Preferably, the sump and the pump 23 areembodied in a unitary structure (see Figs. 1 to 10) General- 1y, the pump 23 has an inlet or suction valve 204 opening from the sump 20 and a pressure discharge valve 203 opening to the line 2| leading to the reservoir 22, and is adapted to be rendered operable and inoperable by pressure responsive means when the pressure respectively falls below a predetermined minimum, and rises to a predetermined maximum. Y'

The pump 23, in its preferred form, comprises a cylinder 205and'an axially contractible and extensible bellows piston 206 reciprocable therein to vary the volume of the uid space. The cylluder 205 consists of a cylindrical cup, the closed end of which projects into the sump chamber |42,

having an elongated cylindrical wall anchored at.

one end; in the body |43 and extending at the outer end into spaced concentric relation into the cylinder 205. `To provide a suitable anchor for the lpiston206, a bore2|| is formed in the body |43 to open from a chamber 2|2, closed by the cover |68 vand separated from the chamber |61 by a partition 2|4, to the interior of the cylinder 205, and is enlargedv at the outer end to define an annular shoulder2l3. The'xed end of the bellows piston 206 `extends snugly through the inner end portion of theborev2| I, and `is formed with athickened outer peripheral flange 2|5 seated1 against` the shoulder 2|3. Positioned againstthe ange 2|5 in fthe enlarged outer end of the bore `2|| is an annular-ring 2|6. A tube 2|] .extends through they ring 2 I5 and in concentrically spaced relation into the bellows piston 206, and has av peripheral mounting ange 2|8 seated on ,the ring 2|6. A ring nut 2|9 is removably threaded into -theouter end of the bore 2|| againstthe `flange 2li?,` and serves to hold the parts `in assembled relation,-with the rubber flange under a heavy deiiectionpressure, and the tube 2|1 clamped in position.

vThe movable yen d of the r,bellows piston 2061s cl osed -by-` a wall 220, andseated against the interior .thereof is `a circularfhead 22| having an axial stem,Y 222 telescoping with the free end of the-tube2l1.` A square wire coil spring 223 encirclesv the tube 2|1k and abuts at opposite ends against ,the ,ring 2|6 -and the head 22|. 'Ihe springf223 is .held` against buckling by the tube 2|1. and serves vto reenforce the peripheral wall of`A ythe bellows,V pistonk 206 against diametrical` contractionfby `the external liquid pressure so f astto maintain va substantially constant piston area., It beevidentthat the bellows piston 206 istof' constant diameter, and is axially extensible` and contractiblev .To reduce heating due to internal molecular friction, both thebellows piston 206, and the spring223 `are of substantial length in relation to the extentof the piston mQVemellt f 1 `f Toprovide means for; actuating the piston, a

rod-..224` isltlireaded yat one end into ythe stem" 222,"an'd extends from the tube 2|1 through the nut 2|9, the chamber 2|2 and an opening 225 in the cover plate |68 for a power drive. A bellows 226, connected at opposite ends to the cover plate |68 and the rod 224, provides a seal Ifor the opening 225. Preferably, the spring 223 is of the compression type, and the piston -rod 224 (see Fig. 1) is reciprocable -by a strap eccentric 221 driven through gearing 228 from the cam shaft 229 of the engine 24.

\Formed in the body |43 is an arcuate valve chamber 230 which is connected intermediate its ends through a passage 23| to the interior of the cylinder 205. The pressure or discharge valve 203 opens from one end of the cham-ber 230 to a. pressure chamber 232 formed in the end of the body |43 and closed by the cover |68 for connection to the line 2|, and the suction valve 204 opens from the chamber |61 to the other end of the chamber 230.

In the present instance, the pressure 'valve 203 230 and 232, and formed with a central valve passage 235. A rubberring or insert 236 is fitted 'into anl annular notch 231 in the outer end edge of the passage 235, and denes a resilient valve seat. .Engageable with the seat 236 is a valve member in the form of a disk 238 having an annular flange 239 defining a valve face, and havingan axial stem 240 extending reciprocably through the passage 235. Preferably, the stem 240 consists of perpendicular plates with intertting slots and riveted at one end to the disk 238. A disk 24| is removably secured to the other end of the stem 240, and serves as a seat for a coil compression spring 242 engaging the nut 233 and tending to close the valve 203 against the pump discharge.

The suction or intake valve 204 is similarly constructed. Thus, it comprises a nut 243 threadediinto the outer enlarged end of a bore 244 connecting the chambers |61 and 230, and

formed with a central valve passage 245. A re- `silient valve seat 246 is tted in the inner face of the nut 243, and is engagea-ble =by an -annular flange 241 on a disk 240 having a stem 249 extending reciprocably through the passage 245. A coiled compression spring 250 acting at opposite ends against the nut 243 and a disk 25| removably secured to the outer end of the stem 240 tends to close7 the valve 204 against the pump suction.

The pump is adapted to be rendered inoperable by automatically holding the intake valve' 204 open. In the present instance, the means for this purpose comprises an over-center device 252 (see Figs. 8 and 9) operable by a pressure responsive device 253 subject to the pressure in the discharge'line 2| of the pump.

The over-center device 252 comprises a base plate 254 removably bolted to the floor of the chamber |61, andformed with upstanding brackets 255 and 2 56. Pivotallymounted on these brackets respectively are an upstanding pawl 251 with a tooth 258, and -a depending pawl 259 with a sive device 253 which in the preferred form comprises a closed cup 212 projecting into the sump chamber |42 alongside rthe cup 205 and defining l an internal pressure chamber 213 opening through a passage 214 to the chamber 232. The upper end of the cup 212 extends through an opening 215 in the plate |64, and has a ilange 216 held by the latter against the gasket 2|0.

Disposed within the cup 212 is a. pressure responsive piston element in the form of a cylindrical rubber bellows or cup 211. One end of the -bellows 211 is closed and,movable, and the other end is iixed to the body |43. In the present instance, the fixed` end oi the bellows 211 extends into a bore 218 opening through the body |43 to the chamber |61 and has a thickened peripheral flange 218 clamped under a heavy deflection pressure against a shoulder 280 in the bore by a ring 28|. A ring nut 282, threaded into the enlarged outer end oi the bore 216, serves to hold the ring 28|! in place. To maintain a constant axial pressure area, a disk 283 with a central stem 284 is disposed against the inside of the movable end wall of the bellows 211, and a coiled compression spring 285 engages at opposite ends against the disk 283 and ring 20| and alfords a, reenforcement for the peripheral wall against diametrical displacement by the external pressure. The actuating rod 21| for the over-center device 252 extends freely through anopening 286 in the base plate 254, the nut 282, ring 28| and spring 28| into the bellows'211 and is threaded into the stem 284 for axial movement therewith.

Fig. 9 illustrates the pump in operative condition. As the discharge pressure rises. the bellows 211 will be longitudinally compressed. and the rod 21| will be lifted accordingly. Upon reaching a predetermined maximum pressure, the rod 21| will Lbe shifted suiciently to snap the lever 266 downwardly to bring the uppermost serration 261 into engagementV with the pawl tooth 266. As a result, the lug 268 will move the operative end of the lever 264 downwardly until the lowermost serration 265 engages the pawl tooth 258, thereby opening the valve 204 and maintaining it in open position.

Upon a decreasein pressure below a predetermined minimum, the spring 205 will lower the rod 21| suiliciently to reverse the operation of the over-center device 252. Thus, the lever 266 will lift the lever 264 against the action of the spring actuated pawls 251 and 259 past the tooth 258 to release the valve 204.

' Rsum component elements being readily accessible.

All of the movable operating parts exposed to the brake liquid are hermetically sealed to prevent leakage and the inilltration of air.

I claim as my invention:

1. A hydraulic .power brake comprising, in combination, a hermetically sealed liquid pressure reservoir containing a pressure maintaining body of gas out of direct contact with the liquid, a hermetically sealed liquid sump for maintaining a reserve quantity of liquid under a low initial pressure, a hermetically sealed power driven pump having a suction line with an inlet check valve opening from 'said sump and having a delivery line with an outlet check valve leading to `said reservoir, means including a hermetically sealed element responsive to the delivery pressure for said pump for automatically holding said inlet check valve open when said delivery pressure attains a predetermined maximum and for releasing said inlet check valve when said delivery pressure drops to a predetermined minimum, a hermetically sealed control unit having a distributing chamber with a pressure valve opening ,from said delivery line and a release valve opening to said sump. a hermetically sealed brake actuator connected to said chamber, a compound valve actuator in said chamber and movable out of release position to close said release valve and open said pressure valve, a manual element for operating said valve actuator, a hermetically sealed pressure responsive reaction element exposed to the pressure in said chamber and acting on said manual element to resist movement thereof out of release position with a force proportional to the liquid pressure, and a hermetically sealed pressure responsive control element exposed to the pressure in said chamber and tending to adjust said valve actuator independently of said manual element to close said Dressure valve' at a predetermined brake pressure corresponding to vthe extent of movement oi said manual element out of release position.

2. A hydraulic power brake comprising, in combination, a hermetically sealed liquid pressure reservoir, a hermetically sealed liquid sump for maintaining a reserve quantity of liquid, a hermetically sealed power driven pump having a suction line opening from said sump and having a delivery line leading to said reservoir, means for controlling the delivery of said pump to maintain a predetermined pressure range in said reservoir, a hermetically sealed control unit having a distributing chamber with a pressure inlet valve opening from said delivery line and a release valve opening to said sump, a hermetically sealed brake actuator connected to said chamber, a

compound valve actuator in said chamber and movable out of release position to close said release valve and open said pressure valve, a manual element for operating said valve actuator, a hermetically sealed pressure responsive reaction element exposed to the pressure in said chamber and acting on said manual element to resist movement thereof out of release position with a force proportional to the liquid pressure, and a hermetically sealed pressure responsive control element exposed to the pressure in said chamber and tending to adjust said valve actuator inde-V pendently of said manual element to close said pressure valve at a predetermined brake pressure corresponding to the extent of movement of said manual element out of release position.

3. A hydraulic power brake comprising, in combination, a brake actuator, a sump, a pressure reservoir, a pump having an inlet line opening from said sump and a delivery line opening to said reservoir and having valve means for controlling said lines, a control unit connected to said actuator and having a supply line opening from said reservoir and an outlet line opening to said sump and having control valve means for controlling said supp'ly and outlet lines, manual means for actuating said control valve means to close said outlet line and open said supply line for brake application and to close said supply line and open said outlet line for brake release. and pressure responsive means automatically operable on brake application to actuate said control valve means independently of said manual means so as to effect the closing of both said supply and outlet lines when the braking pressure attains a predetermined value corresponding with the position of said manual means.

4. A hydraulic power brake' comprising, in combination, a brake actuator, a sump, a pressure reservoir, a pump having an inlet line opening from said sump and a delivery line opening to said reservoir and having valve means for controlling said lines, a control unit connected to said actuator and having a supply line including va. pressure valve opening from said reservoir and an outlet line including an exhaust valve opening to said sump, manual means for actuating said valves to close said outlet line and open said sup ply line for brake application and to close said supply line and open said outlet line for brake release, and pressure responsive means automatically operable on brake application to actuate said valves independently of said manual means so as to eiect the closing of both valves when the braking pressure attains a predetermined value corresponding with the position of said manual means.

5. A hydraulic power brake comprising, in combination, a liquid pressure reservoir, a liquid sump for maintaining a reserve quantity of liquid,

a power driven pump having a suction line open` ing from said sump and having a delivery line leading to said reservoir, means for controlling the delivery of said pump to maintain a predetermined pressure range in said reservoir, a control unit having a distributing chamber with a pressure inlet valve opening from said delivery line and a release valve opening to said sump, a brake actuator connected to said chamber, a compound valve actuator in said chamber and movable out of release position to close said release valve and open said pressure valve, a manual element for operating said valve actuator, a pressure responsive reaction element exposed to the pressure in said chamber and acting on said manual element to resist movement thereof out of release position with a force proportional to the liquid pressure, and a pressure responsive control element exposed to the pressure in said chamber and tending to adjust said valve actuator independently of said manual element to close said pressure valve at a predetermined brake pressure corresponding to the extent of movement of said manual element out of release position.

6. A hydraulic power brake comprising, in combination, a hermetically sealed brake actuapump having an inlet line opening from said sump and a delivery line opening to said reser- Voir and having valve means for controlling said tor, a hermetically sealed sump, a hermetically sealed pressure reservoir, a hermetlcally sealed lines, a hermetically sealed control unit connected to said actuator and having a supply line including a pressure valve opening from said reservoir and an outlet line including an exhaust valve opening to said sump, manual means for actuating said valves to close said outlet line and open said supply line for brake application and to close said supply line and open said outlet line for brake release, and a hermetically sealed pressure responsive means automatically operable on brake application to actuate said valves independently of said manual means so as to effect the closing of both valves when the braking pressure attains a predetermined value corresponding with the position of said manual means.

7. A hydraulic power brake comprising, in combination, a liquid pressure reservoir containing a pressure maintaining body of gas out of direct contact with the liquid, a liquid sump for maintaining a reserve quantity of liquid under a low initial pressure, a power driven pump having a suction line with an inlet check valve opening from said sump and having a delivery line with an outlet check valve leading to said reservoir, means including an element responsive to the delivery pressure for said pump for automatically holding said inlet check valve open when said delivery pressure attains a predetermined maximum and for releasing said inlet check valve when said delivery pressure drops to a predetermined minimum, a control unit having a distributing chamber with a pressure Valve opening from said delivery line and a release valve opening to said sump, a brake actuator connected to said chamber, and means for actuating said control unit, said means being operable in one direction to open said pressure valve and to close said release valve and in the other direction to close said pressure valve and to open said release valve. i

HOWARD D. COLMAN.

10 CERTIFICATE OF CORRECTION.

a. Patent No. 2,2h6,667. June 2LT, 19in.

HOWARD D. COLMAR. It is hereby certified that error appears inthe above numbered patent requiring correction as vfollows: In the grant, lines l and 15, and in thev y heading to theA printed specification, line 5, name of' inventor, for "Howard D. Coleman" read --Howard D. Colman; page 9, second column, lines lbr and 15,'c1aim 6, strike out the syllable and words "tor, a hermetically sealed sump, a hennetically sealed pressure reservoir, ahermetically sealed" and insert the same before "pump" in line 1l, same claim,- and that the said Letters Patent should be read with this correction therein that the same may conform tothe record of the case in the Patent Office. A

Sigled and sealed this 50th day of September, A. D. 1911.1.

Henr'y Van Arsdale, (Seal) Acting Commissioner of Patents. 

